Why extra payments work so well on a mortgage
A mortgage is the longest and largest loan most people ever take on, typically 15 or 30 years and often hundreds of thousands of dollars, so interest has the most time of any common debt to accumulate. In the first years almost all of your payment goes to interest and barely touches the balance. Anything extra you add skips straight to principal, and because the loan has 20 or 30 years left to run, that early reduction compounds into a large interest saving by the end.
The structure of a 30-year loan is what makes this so dramatic. On a $320,000 mortgage at 6.5%, the first monthly payment of roughly $2,000 includes around $1,730 of interest and only about $290 of principal. A $200 overpayment in that first month nearly doubles the principal you retire, and because that $200 of balance never accrues interest again across the remaining 359 months, the saving is far larger than the $200 itself.
How many years could you knock off?
On a typical 30-year mortgage, an extra one or two hundred dollars a month often moves the payoff date forward by four to six years and saves tens of thousands of dollars in interest. With a $320,000 balance at 6.5%, adding $200 a month commonly clears the loan around five years early and saves well over $80,000 in interest across the life of the loan. The exact figure depends on your balance, rate, and how early in the term you start.
The earlier you begin, the larger the prize, because overpayments made in years one to ten remove balance that would otherwise have compounded for decades. The same extra payment started in year 20 still helps, but saves a fraction as much. Use the calculator above to try different extra amounts and starting balances and watch the payoff date and total interest update instantly.
Recasting, refinancing, or just paying extra
Paying a steady extra amount each month is the simplest way to shorten your mortgage and needs no paperwork, no fees and no credit check. You keep your existing rate and payment and simply send more toward principal, which is exactly what this calculator models. Most servicers let you do this through your online account, though it is worth confirming the extra is applied to principal rather than parked as a prepaid future installment.
Recasting is different: after you pay a lump sum, the lender re-amortizes the remaining balance over the original term, which lowers your required monthly payment but does not shorten the loan. It usually costs a few hundred dollars. Refinancing replaces the loan entirely with a new rate and term, which can make sense if rates have fallen far enough to cover the closing costs. For most borrowers who just want to be mortgage-free sooner, a regular extra payment is the cheapest and most flexible route, and you can stop or change it at any time.
Watch for overpayment caps and escrow
Before you commit to a plan, check two things in your mortgage paperwork. First, some fixed-rate deals cap how much you can overpay each year or charge an early-repayment fee, although many US conventional loans allow unlimited principal payments with no penalty. Second, your monthly payment usually bundles principal, interest, property taxes and insurance into an escrow amount, so make sure any extra you send is flagged as a principal-only payment and is not absorbed into next month's escrow.
It is also worth weighing overpaying against other priorities. If you have higher-rate debt such as a credit card or a car loan, that debt almost always deserves your spare money first. If you lack an emergency fund, building one usually comes before locking cash into home equity, since money paid into a mortgage is hard to get back without selling or borrowing against the house.
Biweekly payments and other simple tactics
A popular way to overpay without thinking about it is the biweekly schedule: instead of one monthly payment, you pay half that amount every two weeks. Because there are 52 weeks in a year, you end up making 26 half-payments, which is the equivalent of 13 full monthly payments rather than 12. That one extra payment a year, applied to principal, typically shaves several years off a 30-year mortgage on its own.
If your lender does not offer a true biweekly plan, you can get the same effect by adding one twelfth of your payment to each monthly amount, or by making one extra full payment whenever you can. Rounding your payment up to the next hundred dollars is another low-effort option. Whatever method you choose, the calculator above lets you enter the equivalent monthly extra and see the payoff date and interest saving for your own balance and rate.
A worked example on a $320,000 mortgage
Start with the figures on this page: $320,000 owed at 6.5%, a $2,100 monthly payment, and $200 extra. The monthly rate is 6.5% divided by 12, about 0.542%. In month one, interest is $320,000 times 0.00542, roughly $1,733. That leaves only about $367 of your $2,100 payment to reduce the balance, which shows just how front-loaded a mortgage is. Adding $200 extra lifts the principal portion to about $567 in that first month, more than half again.
Because the loan has hundreds of months left to run, that early head start matters enormously. The $200 of balance you retire in month one avoids 6.5% interest for the entire remaining term, and the same is true of every overpayment after it. Put these numbers into the calculator above and you will typically see the mortgage paid off around five years early with well over $80,000 of interest saved. The single biggest lever is starting early, while the most interest is still ahead of you.
| Extra/month | Payoff time | Interest paid | Time saved | Interest saved |
|---|---|---|---|---|
| $0 (required only) | 27 yr | $358,447 | — | — |
| $100 | 24 yr | $311,485 | 3 yr | $46,962 |
| $200 (this page's default) | 21 yr 8 mo | $276,452 | 5 yr 4 mo | $81,995 |
| $300 | 19 yr 10 mo | $249,089 | 7 yr 2 mo | $109,358 |
| $400 | 18 yr 3 mo | $227,013 | 8 yr 9 mo | $131,434 |
Frequently asked questions
- Should I pay off my mortgage early or invest instead?
- If your mortgage rate is higher than what you could reliably earn after tax by investing, overpaying often wins, and it is a guaranteed, risk-free return. If your rate is very low, investing the difference may come out ahead. This tool only shows the mortgage payoff math and is not financial advice.
- Are there penalties for paying my mortgage off early?
- Some mortgages, particularly fixed-rate deals, cap how much you can overpay each year or charge an early-repayment fee. Many allow overpayments of up to a set percentage of the balance per year with no penalty. Check your mortgage terms before committing.
- Does overpaying lower my monthly payment or shorten the term?
- By default, paying extra keeps your monthly payment the same and shortens the term, which is what this calculator models and what saves the most interest. If you ask your lender to recast, they instead lower the required payment while keeping the original term.
- How accurate are these numbers?
- The calculation assumes a fixed rate and consistent monthly payments, compounded monthly. Your actual statement may differ a little because of rounding, payment timing, or rate changes. Use these figures as a guide, not a lender quote.
- Is this financial advice?
- No. This tool only shows the payoff math for the numbers you enter. It does not account for your wider finances, and it is not advice. The figures from your lender are the ones that count.